Colour or tonal reproduction



y 1961 G. s. J. ALLEN ETAL 2,993,953

COLOUR OR TONAL REPRODUCTION 2 Sheets-Sheet 1 I It w II l 1 mm? 9% wowmm w? %m mww @W m ow m mw wb v a g! a mo w Q Q a m m mad Filed April 22,1957 Inventors Attorney 2 93 953 G. s. J. ALLEN ETAL COLOUR OR TONALREPRODUCTION 2 Sheets-Sheet 2 WEE-- D mom QWN N QWN oN wm @UQNM, Syn

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M Attorney NN MN 7 w wt .5 wow E a a 9%; l U mwwwb m 6E nite States Thisinvention relates to a scanning system for use in colour and tonalreproduction and has a particular application to colour correction inthe production of sep aration negatives or positives for use in colourreproduction.

For colour printing, an original is generally photographed through anumber of colour filters to produce colour separation negatives, andthese are used to prepare printing cylinders or plates for the differentcolours to make multi-colour prints. However, it isknown that theseparation negatives, or the positives made from them, are not usuallysuitable for the preparation of printing surfaces directly, owing to thedifliculties of obtaining colour filters and inks of suitablecomplementary colour response. For example, a printing ink which isnominally cyan may also reflect some light in the magenta part of thespectrum, so that, where both inks are printed at a given element of thepicture, the weight of magenta ink applied should be reduced by anamount dependent on the amount of cyan ink applied.

Accordingly, it is known to correct each element of the colourseparation positive or negative of each colour in accordance with thevalues of each of the other colours present in that element.

In our British patent specifications Nos. 737,768 and 738,118 there aredescribed methods of obtaining colour separation prints for use inmulti-colour reproduction, in which a single light source, modulated inintensity in accordance with the output of an electrical computer,serves both to scan a colour separation print to expose the latter andto scan colour separation negatives or a colour transparency, from whichcolour correction information can be derived, to obtain correspondingelectric signals, that part of the modulation of these signals which isdue to the modulation of the intensity of. the light source beingremoved and the resultant signals, representing the information obtainedfrom the colour separation negatives or the colour transparency, beingapplied to the computer, which is so arranged that its output varies inaccordance with the required colour correction.

A number of advantages result from the use of a single light source forboth analysis and reproduction, as described in these specifications. Inaddition to the economy of apparatus and the removal of a number ofsources of failure and distortion, the problem of maintaining registerbetween two scanning spots, in a system using a first scanning spot foranalysis and a second scanning spot for reproduction, is eliminated. Insysems in which the print is exposed through a separation negative orpositive, however, there remains the difliculty of providing a suitableoptical system for focussing the scanning spot of light, rays from whichpass through the negative or positive, on to the print to be exposedwhile maintaining the spot of small dimensions.

According to the present invention in a method for reproducing tones orcolours in which a single light source, modulated in accordance with theoutput of an electrical computer, serves both to scan uncorrectedtransparencies to provide information from which the required correctioncan be computed and to expose an emulsion in accordance with thecorrected information, Separate scanning beams from the light source aretransmitted through a number of uncorrected transparencies and fall on anumber of light-sensitive devices. The modulated electric signals fromthe latter are applied to the electrical computer in which the requiredcorrection is computed from the signal variations, the emulsion to beexposed being located behind the uncorrected transparency for which thecollection has been computed so that the light transmitted through thelatter passes through the said emulsion on its way to the correspondinglightsensitive device. Such a system has the advantage that no opticaldevices are required to form an image of the uncorrected separationprint on the emulsion being exposed, since the two are in contact, orseparated only by a screen or mask.

Although the invention is primarily concerned with colour correction inmulti-colour reproduction, it can also be used for tonal correction insingle colour reproduction, or in the improvement of resolution orsharpness correction in multi-colour or single colour reproduction,because the scanning spot can be made slightly larger than theresolvable elements in the picture, the operation being thus similar tophotographic unsharp masking. In the application of the invention tocolour correction the uncorrected transparencies will be the separationnegatives or positives.

The light source is preferably pulsating in nature, in order to providealternating electric signals for the computer, and may beamplitude-modulated or time-modulated.

:In one form of the invention a signal from a photomultiplierrepresenting a correcting colour is subtracted directly from a signalfrom a photomultiplier corresponding to the colour to be corrected. Thissubtraction removes to some extent the modulation in the signal which isdue to the modulation of the light source. This arrangement has beenfound to give good colour correction. An alternative method is to passthe signals from the photomultipliers through logarithmic conversioncircuits, the output signals from which represent density values. Ifnecessary, the modulation due to the light source can be removed byexposing a further light-sensitive device to the face of the cathode raytube and passing the output through a logarithmic circuit, the signalfrom which is then subtracted from the signal derived from thelogarithmic circuits associated with the colour chan nels. In a furtherembodiment the demodulating signal is obtained from the computer whichis used to modulate the light output of the cathode ray tube.

The invention may also be applied to the production of screenedpositives or negatives, for example by inserting a contact screenbetween the emulsion to be exposed and the corresponding transparency.

The source for the scanning spot of light may be obtained in variousways, for example from a mechanical system involving a rotating mirrordrum. -In such a system, a small lamp of high luminous intensity isplaced at the focus of a lens which forms a beam of parallel rays. Thisbeam falls on a rotating mirror drum and is reflected through a secondlens, to bring it to a focus to form a spot image. In this way the spotis caused to scan repeatedly along a straight line. If the lamp is nowmoved slowly in a direction parallel with the axis of the drum, spotimage is caused to produce a complete raster scanning a rectangulararea.

However, the most convenient source for the scanning spot is the screenof a flat-faced cathode ray tube, on which a complete raster is producedby means of the usual electrostatic or electromagnetic deflectionarrangements. This has the advantage of virtual lack of inertia.

In order that the invention may be better understood, severalembodiments thereof will now be described, by

3 way of example, with reference to the accompanying drawings, in which:

FIGURE 1 shows diagrammatically an embodiment of the invention in whichthe signals in the colour chan nels are converted to represent densityvalues before being applied to the computer;

FIGURE 2 shows diagrammatically an embodiment in which the colourchannel signals are applied to the computer in a form in which theyrepresent transmission values directly; and

FIGURE 3 shows the use of a contact screen to produce a screenedpositive or negative.

In FIGURE 1 there is shown a cathode ray tube 6, constituting the lightsource, provided with deflection coils 8 connected to time base circuits10, which produce a rectangular raster on the tube face, and with afocussing coil 12 connected to a focussing circuit 14. The intensity ofthe light spot on the face of the cathode ray tube is governed by thesignal which is applied by way of conductor 16 to the grid of the tube.This signal passes through a gate circuit 18 which is controlled by asquare-wave generator 20 oscillating at a convenient high frequency, andas a result the light spot on the face of the tube is pulsating incharacter. The signals derived from light-sensitive devices exposed tolight from the face of the cathode ray tube are therefore alternatingsignals, and the design of the subsequent circuits is considerablysimplified.

Light spot from the scanning spot on the face of the tube 6 passesthrough a lens 22 and a part of this light is deflected by partiallysilvered mirrors 23 and "24 on to the red and green separation negatives25R and 25G, the remainder of the light from the lens 22 passingstraight through to the separation negative 258. The emulsion 26 to beexposed is placed behind and in contact with the correspondingseparation negative, in this case the negative 25B. The emulsion 26 isbacked by a filter 28 such that it passes only light to which theemulsion is insensitive, that is to say, it prevents the transmission oflight to which the emulsion is sensitive. This prevents unwantedexposure of the emulsion due to light reaching the latter through theback surface of the photographic plate. Assuming the emulsion to besensitive only to the blue end of the spectrum, the backing 28 absorbsblue light but transmits light in the remainder of the spectrum.

Light passing through the separation negative 25B and the photographicplate 26-28, is collected by a lightintegrating unit 32B and directed toa photomultiplier 34B, the output of which passes through a cathodefollower circuit 36B.

The light passing through the separation negative 253 is diffused by theemulsion of the photographic plate 2628, and diffusing plates 30R and306 are placed behind the separation negatives 25R and 25G to diffusethe transmitted light in a similar manner. Light-integrating units 32Rand 32G are placed between the diffusing plates and photomultipliers 34Rand 346, the signals from which are applied to cathode followers 36R and36G. The cathode follower circuits 36R, 36B and 36G are included inorder to provide a low output impedance.

The signals from the cathode followers are applied to logarithmiccircuits 38R, 38B and 38G, respectively, which provide output signalsrepresenting the logarithms of the input signals. As an example, eachlogarithmic circuit could consist of a high resistance in series with agermanium crystal rectifier. With this arrangement the current throughthese two components is substantially proportional to the input voltage,and the output voltage appearing across the rectifier is proportional tothe logarithm of the current flowing through it, and hence to thelogarithm of the input voltage. The photomultipliers provide signalswhich are proportional to the product of the brightness of the spot onthe face of the tube and the transmission factor of the element of thecorresponding uncorrected negative which is being scanned at the instantin question. The output of the logarithmic circuits therefore representsthe sum of the logarithms of the spot brightness and the transmissionfactor of the scanned element of the corresponding separation negative.The logarithm of the transmission factor is proportional to the inversedensity of the negative.

To enable the modulation which is due to the intensity variation of thelight spot to be removed from the colour channel signals a photoelectriccell 40 is exposed directly to light from the face of the cathode raytube and its output signal is applied through a cathode follower 42 to alogarithmic circuit 44 similar to the circuits 38R, 38B and 38G. Theoutput of the logarithmic circuit 44 is applied with the output ofcircuit 38G to a subtracting circuit 466, which therefore provides anoutput signal representing the logarithm of the transmission factor ofthe scanned element of the separation negative, that is to say, theinverse density of the scanned element. This output signal is thereforesuitable for the preparation of a magenta printer (uncorrected) for thesubtractive printing process. Similarly the output of logarithmiccircuit 44 is subtracted from the signals derived from circuits 38B and38R in subtracting circuits 46B and 46R to provide signals suitable forthe preparation of yellow and cyan printers. The circuits 46G, 46B and46R may each consist of a T-resistance network, the two signals beingapplied to the two arms of the network, the signal to be subtractedbeing applied in a negative sense. The output signal, representing thedifference, is then taken across the common resistance of the network.

The output signals from the subtracting circuits are applied directly tomasking circuits 506, 5013 and 5011 and also to inverting andattenuating circuits 48G, 48B and 48R. The inverting and attenuatingcircuit in each channel applies an output signal, suitably attenuated,to each of the two masking circuits in the other channels. Thus,considering the blue filter signal (yellow printer) the signal fromcircuit 46B, which represents the inverse density of the uncorrectednegative or the density of the required printer (neglecting correction),is applied to the masking circuit 50B in which it is combined withinverted and attenuated signals from the green and red filter channels.

The corrected signals from the masking circuits are applied throughcircuits 51R, 51B and 516, for deriving the anti-logarithms of thesignals, to limiting circuits 52R, 52B and 526. These limiting circuitsprevent the brightness of the spot on the cathode ray tube fromincreasing beyond a certain level and may comprise two cathode followersto the grid of one of which the signal pulses are applied, the grid ofthe other receiving pulses of constant height, this height representingthe limiting amplitude. The cathodes of the two valves are connected bya diode and a resistance in series, the diode being so directed thatwhen the signal pulses are less than the simultaneous standard pulsesthe diode conducts and the signal pulses are applied by way of a leadconnected to the junction of the diode and the resistor to the grid ofthe cathode ray tube. When the signal pulses are of greater amplitudethan the standard pulses the diode is non-conducting and the standardpulses are applied through the resistor to the output of the circuit.The signals from the limiting circuits are applied to spot brightnesscompensation circuits 53R, 53B and 53G which compensate for thenon-linearity of the relationship between grid potential of the cathoderay tube and the intensity of the spot on the screen. As thisnon-linearity is different for each of the colours, separatecompensation circuits are required for the three channels.

A switch S4 enables the output from one of the spot brightnesscompensation circuits to be applied through J the gate circuit 18 to thecontrol grid of the cathode ray tube.

In an alternative embodiment the light-sensitive cell 40, cathodefollower 42 and logarithmic circuit 44 are omitted and the demodulatingsignal to be applied to the circuits 466, 468 and 46R is obtained fromthe control grid circuit of the cathode ray tube.

FIGURE 2 shows a simpler embodiment of the invention, but shows thecorrecting circuits for only one channel. In this embodiment the cathoderay tubeand associated circuits, the lens systems and the arrangement ofthe separation transparencies, photographic plate, diffusing plates andphotomultipliers are the same as in FIGURE 1.

Assuming that the blue filter channel (yellow printer) is to becorrected by a signal derived from the green filter channel, the outputof the photomultiplier 34B is applied through the cathode follower 368to a subtracting circuit 56. The output from the photomultiplier 34G isalso applied through the cathode follower 36G to the subtracting circuit56, but passes through an inverting circuit 57. The subtracting circuitmay be a T-resistance network having a common resistance in which thecurrents from the blue filter and green filter channels oppose oneanother. This subtraction process cancels to some extent the modulationpresent in both signals which is due to the modulation of the light spoton the face of the cathode ray tube. The resultant signal rom thesubtracting circuit is applied to a non-linear circuit 58 which limitsthe amplitude of the signals, thereby preventing the brightness of thespot on the cathode ray tube from increasing beyond a certain level.This limiting circuit may be of the same kind as that described inconnection with FIGURE 1. The output of the circuit 58 is appliedthrough a spot brightness compensation circuit 53B and through the gate18 to the grid of the cathode ray tube. As a result, there is formed onthe face of the latter a light mask each element of which has theintensity required to correct the yellow printer separation negative 25Band to form a corrected positive on the photographic plate 2628.

The method according to the invention can be used to carry out theelectronic equivalent of a photographic technique which may be calledsuccessive two-stage masking. Considering the masking of the yellowprinter by the magenta printer, in the photographic process a firstcorrected yellow positive is made by combining the uncorrected yellownegative with a mask which has previously been made by combining theuncorrected yellow negative and the uncorrected magenta negative. Thefirst corrected yellow positive is registered with the uncorrectedmagenta negative to produce a further mask, which is registered with theuncorrected yellow negative to make a second corrected yellow positive.This process can go on indefinitely, the amount of the correctioncarried out becoming progressively less at each stage. In theapplication of the method according to the present invention to thisprocess, the signals from the yellow and magenta channelphotomultipliers are passed through logarithmic circuits and the signalin the magenta channel is demodulated to remove the effect of variationsin spot brightness. The resulting signal in the magenta channel,representing density values of the uncorrected magenta negative, and thesignal in the yellow channel, representing density values of thecorrected yellow negative, are fed in phase opposition to a summingamplifier, the out put of which is fed through an antilogarithmiccircuit and a limiting circuit to the grid of the cathode ray tube.

The method according to the invention can be applied to the productionof screened positives and negatives. FIGURE 3 shows an arrangementemploying a contact screen, which is a thin film having a cyclicallyvarying density pattern in two mutually perpendicular directions, toproduce corrected screened positives or negatives. The contact screen 62is placed between and in contact with the separation negative 25B andthe photographic plate G 2628. Dots are formed on the resultingphotograph, the area of the dots depending on the total" quantity oflight passing through the original. With this arrangement thesquare-wave generator 20 and the gate circuit 18 become unnecessary.

Alternatively, a ruled screen can be placed between the uncorrectedtransparency and the lens system which focusses light from the lightsource on to the uncorrected transparency, so that the combination of astop in the lens system and the ruled screen provide the requiredvariation of light distribution across the uncorrected transparency andthe emulsion to result in an image in dot form.

In some circumstances it may be desirable to insert a mask between theuncorrected transparency and the emulsion to be exposed, for example tomodify a picture or compensate for a variation in density in thepicture, or to remove part of a picture.

Although the invention has been described in terms of amplitudemodulation, the light source can equally well be time-modulated. Thetime-modulated pulses for application to the grid of the cathode raytube can be obtained by using an oscillator to initiate the reversal ofa trigger circuit, the return of which is delayed to an extent dependenton the amplitude of the amplitudemodulated signals obtained from thecomputing circuits, these signals representing the correction to beapplied In this case the signals from the photomultiplier will beamplitude modulated in accordance with the transmission factor of thecorresponding separation negative but time modulated in accordance withthe variation of the light spot intensity. The light spot modulation canbe removed from the signals by demodulator circuits controlled by pulsesof constant duration, which can be obtained from the oscillator used inthe production of the input signal for the cathode ray tube.

Instead of the beam-splitting part-silvered mirror system shown inFIGURES 1 and 2, the light spot on the face of the cathode ray tube canbe focussed on the three separation negatives by three separate lenssystems, arranged side by side in front of the cathode ray tube.

The production of the corrected positive in contact with the uncorrectedseparation negative, or separated therefrom only by a screen or mask,eliminates the need for a large condenser lens within the imagefor1ningpart of the optical system. In addition it facilitates the use of asingle light source for both analysis and reproduction, with theadvantages of economy and removal of distortion and registrationproblems.

The system as described so far is applicable only to three-colourreproduction. A considerable amount of colour printing is carried out byusing four colours, a black printer being used in addition to the threecolour printers mentioned above. The invention is quite suitable forproducing a black printer transparency by one of a number of differentmethods. In the conventional photographic method of producing separationtransparencies, a black printer positive separation is frequently madedirectly from one of the colour separation negatives without furthermodification. This method can be used in the scanner described above,but it is possible to improve on it by adding or subtracting valuesaccording to the densities of the other two colour separationtransparencies.

In the case where a black printer is to be used the colour correctionsignals will normally be compressed to some extent by a function of theblack printer signal to allow for the neutral component which will beprovided by the black printer.

The method according to the invention is particularly valuable forproducing the black printer since it is more important that theresolution of this printer should be very high. By virtue of its contactprinting nature, the method described above is capable of transferringall the resolution information from one of the colour separationtransparencies to the emulsion which will form the black printer,

We claim:

1. Apparatus for reproducing visual images, comprising a light source, anumber of uncorrected transparencies, means co-operating with said lightsource for scanning said uncorrected transparencies simultaneously andin synchronism, element by element, light-sensitive means behind saidtransparencies which convert the light passing through saidtransparencies into electric signals of corresponding magnitude, anelectrical computer means arranged to receive said electric signals andto generate an electrical correction signal representing the correctionrequired for the scanned element of one of said uncorrectedtransparencies, means for applying said correction signal to said lightsource to modulate the latter in accordance with said correction, and anemulsion to be exposed placed behind and substantially in contact withsaid uncorrected transparency for which the correction has beencomputed, so that light passing through said uncorrected transparency tothe light-sensitive means associated therewith also passes through saidemulsion and exposes it in accordance with corrected light values.

2. Apparatus according to claim 1, including a further light-sensitivedevice arranged to receive light directly from said light source and toprovide a corresponding electric signal, said electrical computerincluding logarithm-deriving circuits receiving as input signals saidsignals from said light-sensitive devices behind said transparencies andfrom said further light-sensitive device and providing electric signalsrepresenting the logarithms of said input signals, means for subtractingsaid logarithmic signal derived from said further light-sensitive devicefrom each of said logarithmic signals derived from the light-sensitivedevices behind the transparencies and for generating output signalsrepresenting the resultants of said subtractions, said electricalcomputer further comprising correction circuits to which said outputsignals are applied.

3. Apparatus according to claim 1 further comprising a backing filterarranged behind the emulsion and substantially preventing thetransmission to the emulsion of light to which it is sensitive.

4. Colour correction apparatus comprising a light source, a number ofuncorrected colour separation transparencies, means co-operating withsaid light source for scanning said uncorrected colour separationtransparencies simultaneously and in synchronism, element by element,light-sensitive means behind said separation transparencies whichconvert the light passing through said separation transparencies intoelectric signals of corresponding magnitude, an electrical computermeans arranged to receive said electric signals and to generate anelectrical colour correction signal representing the correction requiredfor the scanned element of one of said uncorrected separationtransparencies, means for applying said correction signal to said lightsource to modulate the latter in accordance with said correction, and anemulsion to be exposed placed behind and substantially in contact withsaid uncorrected separation transparency for which the colour correctionhas been computed, so that light passing through said uncorrectedseparation transparency to the light-sensitive means associatedtherewith also passes through said emulsion and exposes it in accordancewith corrected light values, said exposed emulsion serving, afterdevelopment, for the production of a printer for the correspondingcolour.

5. Apparatus according to claim 4, in which said electrical computerincludes means for dividing said signals from said light-sensitivedevices one by another to produce colour correction.

6. Apparatus according to claim 5, in which said dividing means includeslogarithm-deriving circuits for producing electric signals representingthe logarithms of the signals from said light-sensitive devices, andmeans for subtracting one said logarithmic signal from another.

7. Apparatus according to claim 4, in which difiusing plates are placedbehind said uncorrected separation transparencies from which saidcorrection signals are derived, said plates diffusing light transmittedthrough said transparencies to the same extent as the light transmittedthrough the transparency corresponding to the colour to be corrected isdiffused by said emulsion placed in contact therewith.

8. Apparatus according to claim 4, in which said light source is acathode ray tube and the correcting signal applied thereto is apulsating time-modulated signal.

9. Apparatus according to claim 4, in which said emulsion which isexposed is a black printer.

10. Apparatus according to claim 4, in which a contact screen is placedbetween said uncorrected transparency and the emulsion to be exposed.

11. Colour correction apparatus comprising a light source, an electricalcomputer means generating an electric correction signal for modulatingsaid light source, a number of uncorrected transparencies, meansco-operating with said light source for scanning said uncorrectedtransparencies simultaneously and in synchronism, element by element,light-sensitive means behind said transparencies which convert the lightpassing through said transparencies into electric signals ofcorresponding magnitude, a further light-sensitive means arranged toreceive light directly from said light source and to provide acorresponding electric signal, said electrical computer means includinglogarithm deriving circuits receiving as input signals said signals fromsaid light-sensitive means behind said transparencies and from saidfurther lightsensitive means and producing electric signals representingthe logarithms of said input signals, means or subtracting saidlogarithmic signal derived from said further light-sensitive means fromeach of said logarithmic signals derived from the light-sensitive meansbehind the transparencies and for generating output signals representingthe resultants of said subtractions, said electrical computer meansfurther comprising correction circuits to which said output signals areapplied and which generate said electric correction signal for one ofsaid uncorrected transparencies, and an emulsion to be exposed placedbehind and substantially in contact with said uncorrected transparencyfor which the correction has been computed, so that light passingthrough said uncorrected transparency to the light-sensitive meansassociated therewith also passes through said emulsion and exposes it inaccordance with corrected light values.

12. Colour correction apparatus comprising a light source, an electricalcomputer means generating an electric correction signal for modulatingsaid light source, a number of uncorrected transparencies, meansco-operating with said light source whereby it scans said uncorrectedtransparencies simultaneously and in synchronism, element, by element,light-sensitive means behind said transparencies which convert the lightpassing through said transparencies into electric signals ofcorresponding magnitude, said electrical computer means includingsubtracting means for subtracting the electric signal representing thecorrecting colour directly from the signal representing the colour to becorrected to provide said corsection signal for one of said uncorrectedtransparencies, and an emulsion to be exposed placed behind andsubstantially in contact with said uncorrected transparency for whichthe correction has been computed, so that light passing through saiduncorrected transparency to the light-sensitive means associatedtherewith also passes through said emulsion and exposes it in accordancewith corrected light values.

13. Apparatus according to claim 12, in which said electrical computerincludes an amplitude-limiting circuit to which the signal from saidsubtraction circuit is applied.

14. Colour correction apparatus comprising a light source, an electricalcomputer means generating an electrio correction signal for modulatingsaid light source, a number of uncorrected transparencies, meansco-operating with said light source for scanning said uncorrectedtransparencies simultaneously and in synchronism, element by element,light-sensitive means behind said transparencies which convert the lightpassing through said transparencies into electric signals ofcorresponding magnitude, in which said electrical computer meansincludes demodulating means for removing from the signal representingthe correcting colour the modulation due to the variation of thebrightness of the light source, and a subtraction circuit forsubtracting said signal from which the said modulation has been removedfrom the signal representing the colour to be corrected, in which signalthe modulation due to the variation of the brightness of said lightsource is still present, the output signal from said subtraction circuitrepresenting the said correction signal which modulates the brightnessof the light source, and an emulsion to be exposed placed behind andsub- 10 stantially in contact with said uncorrected transparency forwhich the correction has been computed, so that light passing throughsaid uncorrected transparency to the light-sensitive means associatedtherewith also passes through said emulsion and exposes it in accordancewith corrected light values.

References Cited in the file of this patent UNITED STATES PATENTS2,710,889 Tobias June 14, 1955 2,740,828 Haynes Apr. 3, 1956 2,757,571Loughren Aug. 7 1956 2,790,844 Neugebauer Apr. 30, 1957 2,799,722Neugebauer July 16, 1957 2,842,610 Crosfield et a1. July 8, 1958 FOREIGNPATENTS 753,340 Great Britain July 25, 1956

